1. Field of the Invention
The present invention relates to a light emitting device, alight source unit made up of a plurality of such light emitting devices and a projector which incorporates the light source unit.
2. Description of the Related Art
In these days, projectors are used in many cases as image projection apparatuses which project screens or video images of personal computers and further images based on image data stored in memory cards on to a screen. These projectors are such that light emitted from a light source is concentrated on a micromirror device called a DMD (Digital Micromirror Device) or a liquid crystal plate for display of a color image on the screen.
In projectors of the type described above, conventionally, projectors using a high-intensity discharge lamp as a light source have been the mainstream of projectors. In recent years, however, there have been made many proposals on light source units which use a solid-state light emitting device such as a light emitting diode or a laser diode as a light source and fluorescent materials for converting high-output light from the solid-state light emitting device into red, green and blue lights, respectively. For example, Japanese Unexamined Patent Publication No. 2004-341105 proposes a light source unit comprising a light emitting diode as a light source and a rotary member including fluorescent materials for converting ultraviolet light emitted from the light emitting diode into visible light.
According to the proposal by Japanese Unexamined Patent Publication No. 2004-341105, three fluorescent material layers are formed on the rotary member which absorb excited light to thereby emit lights of red, green and blue wavelength areas. By rotating the rotary member, ultraviolet light from the light source is shined sequentially to the fluorescent material layers, whereby lights of red, green and blue wavelength areas can be radiated from the light source unit. However, since shining timings of red, green and blue lights are synchronized with the display device, the rotary member needs to be rotated at a predetermined rotational speed, and there has been a problem that the rotational speed cannot be varied linearly or cannot be varied according to the conditions of the rotary member.